The present invention relates to a method for reducing the viscosity of crude oils and crude oil residuum by treatment of crude oil or crude oil residuum with sound waves. The product from the sonic treatment process affords oil with a substantially lower viscosity than the starting oil.
Heavy oils are generally referred to those oils with high viscosity or API gravity less than about 23. The origin of high viscosity has been attributed to high asphaltene and naphthenic acid content of the oils. Viscosity reduction of heavy oils is important in production, transportation and refining operations of crude oil. Transporters and refiners of heavy crude oil have developed different techniques to reduce the viscosity of heavy crude oils to improve its pumpability. Commonly practiced methods include diluting the crude oil with gas condensate and emulsification with caustic and water. Thermally treating crude oil to reduce its viscosity is also well known in the art. Thermal techniques for visbreaking and hydro-visbreaking (visbreaking with hydrogen addition) are practiced commercially. The prior art in the area of thermal treatment or additive enhanced visbreaking of hydrocarbons teach methods for improving the quality, or reducing the viscosity, of crude oils, crude oil distillates or residuum by several different methods. For example, several references teach the use of additives such as the use of free radical initiators (U.S. Pat. No. 4,298,455), thiol compounds and aromatic hydrogen donors (EP 175511), free radical acceptors (U.S. Pat. No. 3,707,459), and hydrogen donor solvent (U.S. Pat. No. 4,592,830). Other art teaches the use of specific catalysts such as low acidity zeolite catalysts (U.S. Pat. No. 4,411,770) and molybdenum catalysts, ammonium sulfide and water (U.S. Pat. No. 4,659,453). Other references teach upgrading of petroleum resids and heavy oils (Murray R. Gray, Marcel Dekker, 1994, pp. 239-243) and thermal decomposition of naphthenic acids (U.S. Pat. No. 5,820,750).
Generally, the process of treatment of a fluid with sound waves is termed sonication or sonic treatment. The main drawback of sonic treatment for viscosity reduction of heavy oils is that the effect is reversible. The viscosity of the sonic treated oil recovers back to the original viscosity of the oil and in some crude oils viscosity of the product after sonication is higher than the starting oil. There is therefore a need to irreversibly reduce the viscosity of heavy oils by sonication so that sonication can be effectively used as a method for viscosity reduction.
It is this aspect of irreversible viscosity reduction by sonic treatment that this application addresses. Provided is a method of irreversibly reducing the viscosity of oil by an acid enhanced sonic treatment process. The product from the acid enhanced sonic treatment process has a substantially lower viscosity than the untreated oil.
An embodiment of the invention is directed to a method for decreasing the viscosity of crude oils or crude oil residuum comprising the steps of:
contacting the crude oil with an effective amount of an acid comprising organic acid, mineral acid or mixtures thereof,
sonicating said acid treated crude oil at a temperature and for a time sufficient to decrease the viscosity of said crude oil or residuum.
Another embodiment of the invention is directed to a crude oil or crude residuum having decreased viscosity prepared by
contacting the crude oil or residuum with an effective amount of an acid comprising organic acid, mineral acid or mixtures thereof,
sonicating said acid treated crude oil or residuum at a temperature and for a time sufficient to decrease the viscosity of said crude oil or residuum.